Replaceable firing pin for mortars



Feb. 19, 1952 c. N. HICKMAN REPLACEABLE FIRING PIN FOR MORTARS.

Filed Nov. 29, 1944 avwe/wtp'b CLARENCE N. HICKMAN 954 Fwd dyad PatentedF eb. 19, 1952 REPLACEABLE FIRING PIN FOR MORTARS Clarence N. Hickman,Jackson Heights, N. Y., assignor to the United States of America asrepresented by the Secretary of War Application November 29, 1944,Serial No. 565,644

3 Claims. 1

The invention described herein may be manufactured and used by or forthe Government, for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to ordnance and more particularly to rifledmuzzle loading ordnance of the mortar classification.

More specifically this invention consists of a new and improved methodfor obtaining adjustments in the range of projectiles fired frommortars. It is well known that the angle of elevation of mortars can bevaried only slightly to produce small changes in range. To acquirelarger changes in range it has been customary to provide the projectilewith the maximum propellent charge necessary to acquire the maximumrange, and to remove portions of this charge, at or about the time ofloading, as changes in range require. The prior art is replete withvarious methods and means for fastening these propellent charges to theprojectile to facilitate easy removal of portions of the charge. Whenstabilizing fins are employed, the charge is preferably supportedbetween the fins to permit easy removal of a portion of the charge toprovide for range adjustments. Notwithstanding these improvements thismethod of range adjustment remains awkward and fails to provide thedegree of precision desired.

By virtue of this invention precise adjustments in range may be easillyattained by changing the density of loading for any number of firingswithout the necessity of making adjustments on each projectile.

The mortar and projectile assembly of this invention consist mainly of aprojectile containing a payload and a propellent charge which may beconsidered as including an ignition cartridge inserted into a containerformed at the base of the projectile and the propellant proper which isformed of a plurality of thin plates of ballistite, or other suitablepowder, which fits over the cartridge container. The projectile ismuzzle-loaded into the barrel of the mortar and is fired when theignition cartride engages a fixed firing pin in the breech end of thebarrel.

As a result of my researches on the 4.2 chemical mortar which wereconducted in an efifort to determine experimentally the optimum webthickness and density of loading for the mortar it occurred to me thatadjustments of the initial volume of the combustion chamber to acquireadjustments of the density of loading might oifer a solution to theproblem of range control for the mortar. By density of loading is meantthe ratio between the weight of the propellent charge and the weight ofthe volume of water which would fill the chamber in which the charge isloaded. Actually a change in the amount of propellant results in achange in the density of loading; however, changes in propellant weightrequire that the propellant on" each projectile be modified and to avoidthis I prefer to maintain a constant maximum charge and obtain changesin the densityof loading by producing changes in the volume of thepowder chamber. of loading decreases the velocity of the projectile andthe maximum pressure within the chamber but increases the length oftravel of the projectile to the point of maximum pressure.

Various methods for acquiring changes in the volume of the combustionchamber logically include varying the length of the cartridgeholder orthe spacing between the various bundles of propellant. However, any ofthese methods necessitate manipulations or adjustments on eachprojectile and would also involve mechanical difiiculties. I considerthat these methods have little to offer over the prior art method ofremoving a portion of the powder charge. It occurred to me that I couldacquire the necessary change in volume for the propellant bychanging-the length of the firing pin within the barrel of the mortar.This method appeared so attractive initially that I immediatelyconducted tests to determine that sufiicient variations in range couldbe obtained by changing the length of the firing pin. I found that achange in range of about 200 yds. could be obtained for each one inchincrease in length of firing pin.

Obviously it is impractical to dismantle the mortar to insert differentlength firing pins every time a change in range is desired, and testsindicate the change in length of firing pin required to produce thedesired change in range is larger than can be accommodated for byadjustments on the mortar barrel. It occurred to me that by making thefiring pin tubular in form so that it may be slidable over the fixedpin, adjustments in pin length could be easily acquired by insertingdifferent length tubular members into the muzzle. I prefer to provide ateach end of the tubular firing pin at least three radially divergentspider vanes for centering the tube withinthe barrel of the mortar.

In the appended drawings forming a part of this specification, there isdisclosed a preferred embodiment of the invention, wherein,

In general, a decrease in density.

Fig. 1 is an elevational view partly in longitudinal section showing thereplaceable firing pin in detail;

Fig. 2 is an elevational end view of Fig. 1; and

Fig. 3 is an elevational view in section showing the replaceable firingpin in assembled position within the mortar barrel.

Referring now to thedrawing and particularly to Fig. l there'is shown atubular member 106i the replaceable firing pin fitted over the fixedfiring pin 9 which projects from the breech end 8 of the mortar barrel1, as illustrated in Fig. 3. The tubular member ID is shown providedwith four fixed centering fins l2 and is threaded internally at itsupper end so asto receive the front end M of the replaceable firing pinwhich has a generally pointed head ll3..adaptedxtolimpact against thepercussion cartridge on a projectile. The front end 14 is also providedwith four fixed fins IE to center the pin. This front end isadjustableinlength by 'virtue of its threaded engagement with the lower portion ofthe pin. The openings H are provided for inserting a rod or other toolwhich may beneeded'to adjust the members in the event the threads becomeeroded by the products of combustion. These openings also permit equalpressure distribution on the inner" and outer surfaces ofthe-replaceable pin.

Fig. '3 shows the removable pin in place within the barrel of themortar. To provide quick removal of these firing pins for substituting apin of" different length, a hooked member may be inserted into themuzzle end of the'barrel for engagement with anyone of the projectingfins.

It should'be understood that I have disclosed only a preferredembodiment of my invention and that I do-not propose to be limitedprecisely to the structure illustrated or otherwise than within thescope of the appended claims.

I claim:

'1. A replaceable, adjustable firing pin for a mortar having a firingpin secured to its breech end, said replaceable firing pin including atubular member and a second member having a pointed head and beingadjustably and mo'vably secured to said tubular member and metallicradially extending means projecting from each of said members forcentering said members within the mortar barrel.

'2. In combination, a mortar barrel having a fixed firing pin and areplaceable firing pin adapted to be slidably inserted in the muzzle ofthe barrel and-around said fixed firing pin; said replaceable firing pinincluding a tubular member and a front end, each of which are providedwith a'pluralit'y'of radially extending flanges of equal length forcentering said pin in said barrel;

saidtubular memberhaving an internal bore of greater diameter than thediameter of said fixed firing pin; said front end being pointed at oneof its end portions and having its opposite end portion reduced incross-section and of adiameter smaller than the diameter of said boreand adapted for insertion in'said tubular member.

3. The combination of claim 2 in which the tubular member and the frontend of the replaceable firing pin are each threadably adapted foroperative connection to each other.

CLARENCE N. HICKMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

FOREIGN PATENTS Number Country Date 521,747 France Mar. "14, 1921348,052 Germany Jan. 30, 1922 299,088 Germany Aug. 17, 1922 585,216France Dec. 4, 1924 352,916 Italy Sept. 25, 1937

